Photoreduction CO2 to hydrocarbons and photosplitting water for H-2 production are the most promising, sustainable approaches for environmental pollution alleviation and solar-to-chemical energy conversion. However, developing low-cost, high efficient and stable photocatalysts remains a great challenge. Herein, we reported a novel visible-light activated MoP co-catalyst loaded g-C3N4 photocatalyst for CO2 reduction and water splitting under simulated irradiation firstly. Experimental results demonstrated that the composites were highly active and exhibited superior stability. The maximum CO and H-2 evolution rates of 0.92 mu mol h(-1) and 40.38 mu mol h(-1) were achieved on MoP/CN-15% catalyst, which were 4.5-fold and 74.5-fold higher than the pure g-C3N4, and the corresponding apparent quantum efficiencies (AQE) were 3.5% and 18.3% at 420 nm, respectively. In situ FTIR analysis disclosed the CO2 adsorption and conversion progress, in which the COO- acted as a major intermediate. Furthermore, comprehensive characterization analysis revealed the introduction of MoP facilitated the separation and transfer of photogenerated electron-hole pairs, and the theoretical calculation by density functional theory (DFT) also confirmed that MoP could effectively separate the photoexcited charges from g-C3N4. Combining with experimental and DFT calculations results, a new way to design cost-effective photocatalysts has been enlightened. (C) 2018 Elsevier Inc. All rights reserved.